A systematic study of the synthesis, physical properties, and reactivity of allylboranes in relation to stereo- and regiocontrolled carbometallation reactions is proposed. Applications to the synthesis of a number of pharmacologically active compounds including antitumor agents and antibiotics are described. Execution of the research is planned in four distinct yet interrelated phases. The first deals with the synthesis of novel allyldialkyl- and allyldiarylboranes, including axially disymmetric reagents. In the second phase, a variable temperature 1H NMR study of the permanent allylic rearrangement process which occurs in these species will be undertaken. By varying substituents on both boron and on the allyly unit we hope to gain greater insight into the factors which determine the regio- and stereochemistry of the predominant allylboron species in solution. The third phase will be devoted to a determination of the scope of the carbometallation reaction towards unsaturated organic substrates. Special emphasis will be placed on the diastereoselectivity achievable in the reaction, especially as it relates to the stereo- and regiochemistry of the allylboranes. Finally, the utility of the developed methodology will be demonstrated by applying it to the synthesis of several compound classes. These include stereo- and regiodefined tri- and tetrasubstituted olefins, C-nucleosides (showdomycin and related antibiotics and antitumor agents), asperline, and ionophore antibiotics. The long-term objective of this project is to achieve a greater understanding of the properties of these allylmetallics and to utilize this knowledge in their development as useful reagents for the stereocontrolled synthesis of organic molecules.